Asthma is a chronic disease in which sufferers have repeated attacks of difficulty in breathing and coughing.There seems to be an increase in the amount of asthma all over the world, especially in children.To understand what happens in asthmatic attacks, it's helpful to visualise the basic structure of the airway tubes of the lung.
The main airway (windpipe, trachea) of the body is about 2 to 3cm across. It divides into its main branches (bronchi), which lead to the right and left lung, which divide further, like the branches of a tree, to supply air to all parts of the lungs.
The smallest tubes (bronchioles) are only millimetres wide and they are made up of ring-shaped muscles that are capable of contracting or relaxing. Anything that makes them contract will narrow the passages, which makes it more difficult for the air to pass through (so making it harder to breathe) and also gives rise to the characteristic wheezy noise that a person makes when they have an asthma attack.
Asthmatics tend to be sensitive to various types of irritants in the atmosphere that can trigger this contraction response from the bronchial muscles. The bronchioles also have an inner lining that becomes inflamed in asthma, which makes the lining swell and produce an excess amount of the mucus (phlegm) it normally makes, clogging up the tubes.
All of these processes contribute to the airway narrowing and the treatment for asthma is aimed at reversing them as much as possible. People of all ages get asthma but 50 per cent of sufferers are children under 10. Asthma is slightly more common among boys than girls. But after puberty the pattern reverses and among adults, women are more likely to develop asthma than men.
Asthma can be triggered by external agents, such as irritants in the atmosphere which are breathed in, or by internal reactions within the body that have been caused by an external influence.
The kinds of provoking factors can be divided into two groups.
To acquire asthma, people seem to need to have been born with a predisposition to the disease. It may not reveal itself until they have been exposed to some asthma irritants.
A mother who smokes, low birth weight, a lack of exposure to infection in early life and traffic fumes have all been associated with the increase in asthma. Less draughty houses resulting in an accumulation of house dust mites and cooking gases may also be part of the problem.
Currently, a great deal of research is being carried out to look for the genes that allow asthma to develop. But until we can prevent asthma, the aim of treatment is to suppress the symptoms and try to avoid the triggers where possible.